Schistosomiasis haematobia is a parasitic disease of international concern, affecting the health of extensive populations, but it is the poorest understood of the schistosome diseases complex. This void in basic knowledge stems from the fact that until recently there have been only limited biomedical investigations on this disease at the laboratory level. An availability of parasites and snails, establishment of tentative parasite-snail and parasite-definitive host, systems have shown promise, however, for alleviation of this medical dilemma. The primary objective of work under the present proposal is to make contributions to the basic biology of S. haematobium and related schistosomes in their molluscan and selected definitive hosts. Emphasis will be on S. haematobium, but investigations will be made on a closely related species, S. intercalatum, to determine how this parasite, biologically (host-parasite relationships, pathobiology, etc.), fits into the S. haematobium terminal spined-egg complex of schistosomes which is becoming of growing medical concern to peoples of Africa. Several species of lower mammals (woodrats, hamsters, opossums) will be employed to evaluate the parasitological parameters of S. haematobium and S. intercalatum as a means for understanding inter-relationships. Accent will be placed on in depth studies of the biology of S. haematobium infections, including basic host-parasite relationships and pathology in 2 species of African nonhuman primates (Cercopithecus talapoin and Erythrocebus patas) which, in primary screening, demonstrated significant potentials as hosts for parasite oncogenesis and biomedical situations comparable to those characteristic to schistosomiasis haematobia in man. This will be a pertinent step in the search for laboratory models.